[S390] kernel: Initialize register 14 when starting new CPU
When starting a new CPU we currently jump to start_secondary() without
setting register 14 (the return address) correctly. Therefore on the stack
frame for start_secondary an invalid return address is stored. This leads
to wrong stack back traces in kernel dumps.
Example:
#00 [1f33fe48] cpu_idle at 10614a
#01 [1f33fe90] start_secondary at 54fa88
#02 [1f33feb8] (null) at 0 <--- invalid
To fix this start_secondary() is called now with basr/brasl that sets
register 14 correctly. The output of the stack backtrace looks then
like the following:
#00 [1f33fe48] cpu_idle at 10614a
#01 [1f33fe90] start_secondary at 54fa88
#02 [1f33feb8] restart_base at 54f41e <--- correct
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 648f642..1b67fc6 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -836,7 +836,7 @@
stosm __SF_EMPTY(%r15),0x04 # now we can turn dat on
basr %r14,0
l %r14,restart_addr-.(%r14)
- br %r14 # branch to start_secondary
+ basr %r14,%r14 # branch to start_secondary
restart_addr:
.long start_secondary
.align 8